Method for applying anti-lacerative film to glass

ABSTRACT

A method for laminating plastic film to glass is provided. The method includes the steps of providing a precast layer of glass on a support and placing a polymer film at a distance therefrom; then providing a ram with a lower surface having substantially the same contour as the top surface of the glass layer and providing a hard, flexible intermediate layer between the ram and the polymer film in which the intermediate layer has a contour that is more convex than that of the lower surface of the ram. The distance between the ram and the precast glass is then decreased such that initially the lower surface of the ram contacts the intermediate layer and the central portion of the intermediate layer contacts the polymer film at its center first and continues to stretch the polymer film into contact with the glass layer at its center outwardly towards the edges. Eventually the pressure is increased between the ram and the glass layer, heat is applied, and the glass layer and polymer film are laminated. The method can also be used to laminate together a polymer film between two glass layers or to laminate together two glass layers with two polymer films, one film between the glass and the other film on the surface of one of the glass layers.

FIELD OF THE INVENTION

This invention relates to laminated glass/plastic film structures, andis particularly directed to apparatus and methods for producing suchlaminated glass/plastic film structures. The invention is directedtowards the production of glass/plastic film structures that arephysically quite large; specifically and particularly, suchglass/plastic film structures as are used for automobile windshields andside windows of automobiles and other vehicles, and indeed of otherglass containing structures. The invention also provides that themulti-laminar glass/plastic film structures may be produced on apparatusand by the methods of the present invention efficiently and at muchlower cost than has previously been possible.

BACKGROUND OF THE INVENTION

The present inventor is the applicant in several previous U.S. patentapplications, specifically Ser. No. 07/315,298 filed Feb. 24, 1989,abandoned, and its divisional application Ser. No. 07/448,286 filed Dec.11, 1989, abandoned. The previous patent applications teach an apparatusand method for laminating a layer of non-oriented polymer plastic to aprecast layer of glass for much the same purposes as described above,and the present invention is particularly directed to improvements inthe apparatus and methods as previously taught.

The automotive glass industry is, so far, highly labour intensive. Forexample, the preparation of a windshield or side window for anautomobile very often requires a hand lay-up of the non-oriented plasticfilm to the glass. After the plastic film has been placed on the glassand perhaps most of the air bubbles caught between the film and theglass removed by use of a squeegee, a vacuum ring or other device may beplaced around the periphery to pull as much air as possible from betweenthe film and the glass. Thereafter, the glass/plastic film combinationmay be placed into an autoclave which is then pressurized and heated soas to adhere the non-oriented plastic film to the glass under pressureand heat conditions.

Most often, in such a structure the plastic film may be a compositelaminar structure of non-oriented polyvinyl butyral together withoriented polyethylene terephthalate (PVB/PET), or it may be a compositelaminar film of non-oriented polyurethane together with polyethyleneterephthalate; or it may be PVB or polyurethane. The polyvinyl butyral(or polyurethane) is a generally soft non-oriented material which isquite often slightly embossed and somewhat opaque because of its surfacecharacter. However, the apparent opacity of the PVB disappears when thefilm surface is smooth, or is made smooth under the action of heatand/or pressure. The polyethylene teraphthalate is an oriented toughfilm which provides anti-lacerative characteristics to the glass/plasticfilm structure, because glass will shatter upon impact. The PVB layeradheres the PET layer to the glass, and also provides energy absorptionin the event of impact with the composite laminar structure. Thus, thePET layer provides a barrier to protect a person from shattered glassshards in the event of an accident.

It is a characteristic of polymer plastic films as discussed herein thatif there are any significantly large air bubbles entrapped in theinterface between that film and glass, they may remain after heat andpressure treatment, particularly as in the prior art. However, if verysmall air bubbles are entrapped, and particularly if the film layer isPVB, they will be absorbed by the PVB. The difficulty is thatsignificant air bubbles at the interface between the PVB and glass, orat the PVB/PET interface, or wrinkles that may occur in the PVB or PET,materially affect the optics of the glass/plastic film laminar structurein that an object viewed through the glass/plastic film laminatestructure may appear to be distorted. This may be especially importantin the event of use of glass/plastic film laminar structures as sidewindows of automobiles or other vehicles, since such windows aregenerally unframed, and the incidence of air bubbles or wrinklesespecially near the edges of the glass is not acceptable.

The autoclave procedure to adhere a non-oriented plastic film to glassrequires several hours per cycle, and it is not possible until the afterthe cycle has finished to determine if the glass/plastic film laminateworkpiece being produced is acceptable. In other words, there is nodetermination of scrap (other than breakage) until after the autoclavecycle has been concluded. Moreover, the amount of unusable workpiecewhich become scrap may be high, so that the prior art autoclaveproduction methods may be significantly inefficient as to the use oflabour, the use of time, and particularly as to the use of energy.

In the meantime, the use of glass to which a polymer plastic film hasbeen adhered as a windshield or as a side window of automobiles and thelike has been approved, and it is expected that such use may becomemandatory. In particular, use of such laminated glass/plastic filmstructures as side windows is a significant safety step as there islittle that can be done to preclude impact of an object against the sidewindow in the event of an accident where there may be relative sidewaysmovement of any object to the side window; whereas the increasing use ofseat belts--the use of which is mandatory in most jurisdictions--and theincreasing use of air bags may reduce the chance of impact particularlyof the head of a driver or passenger against the windshield of anautomobile.

Still further, the production of PVB/PET having uniform thickness isdifficult if not nearly impossible to achieve, because there may forexample be gauge bands produced. Non-uniform thickness of the PVB/PETmay again result in distortion which is visible, even if the distortionhas a gauge thickness in the order of 0.00001 inch.

The above difficulty--eliminating gauge bands for example--can beovercome by bending two pieces of glass together so that they haveessentially the same shape. Thereafter, one of the pieces of glass whichis to be used as a side window for an automobile has the film placed onit. Then, the mating piece of glass may be placed on the film as a coverplate, and a vacuum ring or vacuum bag may be used to withdraw as muchair as possible. After that, the combination of the glass having thePVB/PET film, and the cover plate of glass resting upon the PET, isautoclaved as discussed above. Finally, the structure is removed fromthe autoclave and the glass cover plate could possibly be re-used.

The present inventor has noted that the relatively soft PVB (orpolyurethane) non-oriented plastic film layer may indeed act as a gaugewhen a ram or pusher is being used to press the film against the glass.What this does is to permit a slight adjustment of the glass and thepusher ram acting against it, and this phenomenon occurs as a functionof the temperature and/or pressure working on the PVB. In any event,because cold or warm PVB has a moderate tensile strength, it is possibleto push a ram against the film and to contact it against the glass--thedetails of which are discussed hereafter--so that when the film andglass are fully contacted in a manner that substantially precludes anylarge air bubbles to have occurred, the structure may be heated to thelaminating temperature of the PVB.

Of interest in the prior art is U.S. Pat. No. 4,772,006 issued Sep. 20,1988 to Guglielmetti et al. That patent contemplates multi-laminarglass/plastic film structures that may be glass/PVB/glass orglass/polyurethane/glass. However, the patent is particularly directedto an apparatus whose purpose is to grip and transfer a pre-cut andpre-stored sheet of flexible plastic film to the first layer of glass,after which the second layer of glass is placed on top. There is noparticular or specific teaching of the steps that then follow: thepatent suggests that the stack formation is then brought to an automaticassembly station which is a pressure sealing stage carried out at hightemperature and pressure--in other words, an autoclave.

Two Japanese publications, Number 63/71332 and Number 63/71334, eachpublished Mar. 31, 1988 in the name of Ishikawa and Kurita also referredto multiple laminations, in particular where laminations are placed onboth sides of glass. However, in all events the processes discussed byIshikawa and Kurita are carried out in a vacuum chamber or autoclave andresult in a laminate structure which is sealed at its edges. Ishikawaand Kurita are particularly concerned with the probability of dust beingdeposited between the plastic film and the glass.

The present invention may apply to precast glass which is essentiallyflat, but it is especially adapted for precast glass that is curved suchas for use as windshields and side windows of automobiles. Sometimes thecontour of such precast glass may be quite complex.

As it happens, in a simple laminated structure having glass togetherwith PVB/PET, the composite layer of non-oriented PVB polymer plasticfilm together with oriented PET polymer plastic film is applied to theinside surface of the glass--that is, to the concave side of the curveif the precast glass is curved, which will be the inside surface of thewindshield or side window when in use.

Thus, the apparatus and methods of the present invention apply to theproduction of laminated glass and polymer plastic film whether theprecast glass is flat, has a simple curvature, or a compound curvature.

One of the essential characteristics of the apparatus of the presentinvention is that at least one of the saddle--or at least the face ofthe saddle that is next to the glass when the glass is placed in thesaddle--the ram, or both, should have good heat transfercharacteristics. Thus, when it is desired in practicing the methods ofthe present invention for the glass to be heated up, heat is transferredto the glass through the saddle quite quickly; and likewise, when it isdesired for the glass to be cooled down, heat is extracted from theglass through the saddle quite quickly.

As described hereafter, although it is usual for the heat to betransferred to the glass through the saddle, it is possible to heat andcool the ram, or to heat one of the saddle and the ram and to cool theother. The present invention also contemplates that one of the saddleand the ram--usually the saddle--may be constantly heated, and theother--usually the ram--may be cooled sufficiently as to cause grossheat extraction away from the glass and polymer plastic combination.

Obviously, the surface of the upper side of the saddle must conform tothe surface of the outer curvature of the glass so as to fully supportthe glass. It is possible that the upper face of the saddle may belined, particularly as discussed hereafter.

In any event, if the surface of the saddle has essentially the samecoefficient of heat expansion and contraction as that of glass, then asthe glass is heated up and cooled down there is essentially zeroslippage of the glass with respect to the face of the saddle. Obviously,as the glass is being heated up and cooled down while the ram isexerting pressure against the upper side of the glass, if the glass hasa coefficient of heat expansion and contraction which is significantlydifferent than that of the saddle, then either the saddle or the glasswill expand or contract at a different rate than the other. Since glasshas very little or substantially zero tensile strength, although it hasquite high compression strength, if the saddle is permitted to expandfaster than the glass then there is a possibility that the glass willbreak as it is being heated because the saddle will have expandedfaster. Likewise, if the saddle expands (and contracts) slower than theglass, then there is a likelihood that the glass will break duringcool-down. Such breakage may occur because of the friction between theglass and the surface of the saddle.

It is possible for the surface of the saddle to be coated with amaterial that permits some slippage, such as silicone or PTFE.

As discussed hereafter, the present invention contemplates thatstainless steel--for example stainless steel (compound SS430)--isparticularly useful because it has a coefficient of heat expansion whichis quite similar to that of glass. Alternatively, an aluminum base plate(or a base plate of other metal having high heat transfercharacteristics, such as brass or copper) may be used because of thehigher heat conductivity than that of steel, so that the base plate maybe heated and cooled using appropriate heaters and cooling fluids andthe like, with a stainless steel face being presented against the glassby the top of the saddle.

It is desirable for the surface of the saddle to be machined as closelyas possible to the outside curvature or contour of the glass to beplaced on it. However, because glass is reasonably flexible, at leastordinary manufacturing tolerances in terms of preparation of the surfaceof the saddle may be accommodated.

As discussed hereafter, the present invention also contemplatesmulti-laminar compound structures having two layer of glass with atleast one layer of non-oriented polymer plastic film, one layer oforiented polymer plastic film, and perhaps even two layers ofnon-oriented polymer plastic film. Even in the event of the manufactureof windshields, because of the specific structures of the ram and saddleas discussed in detail hereafter, the apparatus and methods of theinvention are more tolerant of mismatched pairs of glass in suchmulti-laminar structures as contemplated immediately above.

SUMMARY OF THE INVENTION

As noted above, the present invention contemplates the production ofcomplex single or multi-layer glass structures having oriented and/ornon-oriented polymer plastic films. For example, a windshield for anautomobile may comprise laminates of glass, a non-oriented polymerplastic film, and glass; and the non-oriented polymer plastic film maybe one of polyvinyl butyral and polyurethane. Methods and apparatus forproducing such a windshield are provided by the present invention.

Likewise, a safety windshield or side window for an automobile may beproduced in keeping with the present invention, where the safetywindshield or side window comprises laminates of glass, a firstnon-oriented polymer plastic film, glass, and a second non-orientedpolymer plastic film together with PET. The second non-oriented polymerplastic film layer may also be polyurethane; and in any event is placedon the inside surface of the safety windshield or side window when inuse. The PET may also be laminated on that second layer, the PET beingremote from the glass.

Thus, the present invention contemplates a complex bi-layer ormulti-layer structure comprising: glass together with polyurethane; orglass together with polyurethane and PET; or glass together with PVB andPET; or glass together with polyurethane and a further layer of glass;or glass together with PVB and a further layer of glass; or glasstogether with PVB, a further layer of glass, and a further PVB/PET layeror a further polyurethane/PET layer; or glass together withpolyurethane, a further layer of glass, and a further PVB/PET layer or afurther polyurethane/PET layer.

The present invention further contemplates that the apparatus andmethods taught herein can be placed and operated in any orientation.However, for ease of understanding, but not so as to limit the scope ofthe invention, the following discussions assume the apparatus to beplaced so that the principal components are oriented horizontally anddisplaced or moved vertically.

In general, in the following discussions, and in the accompanyingclaims, the words "horizontal" and "horizontally", and the words "firstdirection" or "first orientation" may be read as being synonymous. Thus,it should be emphasized that the words "second direction" or "secondorientation"--where the first and second directions or orientations areassumed to be generally mutually perpendicular--might in somecircumstances also be synonymous with "horizontal" or "horizontally".Therefore, it is to be understood that there may be complete freedom asto the disposition and direction of operation of any of the componentsor the methods of the present invention, and that the followingdiscussion is exemplary and not intended as being restrictive in scope.

As to the apparatus contemplated by the present invention, it comprisesa supporting saddle for the glass, means for positioning a polymerplastic film in a first orientation (usually horizontally) a distanceaway from (usually above) and over the glass when the glass is placed onthe saddle, a ram over the plastic film, and means to effect relativemotion of the ram and the saddle in a first direction (usually vertical)so as to close the (vertical) distance between the ram and the plasticsufficiently as to cause the ram, the plastic film, the glass, and thesaddle, all to be in intimate physical contact seriatim. At least one ofthe saddle and the ram is such that it is able to transmit heat to andabsorb heat from the precast layer of glass which is placed on thesaddle; and the contour of the first (upper) face of the saddle and thecontour of the first (lower) face of the ram are each substantiallyidentical to the respective first (lower) and second (upper) faces ofthe precast layer of glass which is placed in the saddle. At least thefirst (upper) surface of the saddle is of a material which has asubstantially identical coefficient of heat expansion and contraction tothat of the glass. By use of the apparatus as described above, there issubstantially zero slippage that may occur between the contacting first(upper) surface of the saddle and the second (lower) surface of theglass as the glass is heated and cooled during the process of laminatingthe polymer plastic film to its second (upper) surface.

The saddle or the ram, or both, may be heated and cooled so as toquickly transmit heat to and absorb heat from the combination of theglass and the polymer plastic film. Moreover, one of the saddle and theram--usually the saddle--may be constantly heated, and theother--usually the ram--may be cooled sufficiently as to cause grossheat extraction away from the glass and polymer plastic combination.

The polymer plastic film is held or positioned in such a manner that itmay move and change its linear dimensions under the effect of heatand/or pressure being applied to it or to which it is exposed. Thus, thezero slippage condition referred to above is attained.

The discussion hereafter assumes the orientation of the apparatus andthe glass to be as indicated above, without unduly restricting thedisposition and modes and directions of operation of the apparatus.

The means to effect relative vertical motion of the ram and the saddlemay comprise means to lower the ram towards the saddle, or it maycomprise means to lift the saddle towards the ram. In the firstinstance, the saddle is fixed, and in the second instance the ram isfixed. It is preferred for the saddle to be lifted towards the ram so asto avoid placing hydraulic fittings and fixtures of any sort above thesaddle. Almost invariably hydraulic fittings and fixtures will tend toleak; and by not having any potential leak sources above the saddle, thepossibility of hydraulic fluid dropping on to the saddle or on toproduct placed in the saddle is precluded.

Specific features of the apparatus are described in detail hereafter.

Moreover, a further improvement to the apparatus described abovecomprises the provision of a further layer of flexible hard materialwhich is placed below the lower surface of the ram. When the ram ismovable, the extra layer of hard material is clamped so as to be movabletherewith. In any event, an extendible piston is provided that actsagainst the upper side of the flexible material at the centre thereof,so as to flex the flexible material from the centre thereofindependently of the ram, downwardly towards the precast glass when itis placed in the saddle. The piston is force displaced further so thatthe flexible material will progressively contact a larger area of thefilm and glass being laminated to it as the ram is moved downwardlytowards the saddle or the saddle is moved upwardly towards the ram.

The polymer plastic film may be a composite material of non-oriented andoriented polymer plastic films such as PVB/PET or polyurethane/PET, orit may be a single layer of non-oriented PVB or polyurethane--especiallyin the case when it is intended for a further layer of glass to belaminated to the structure.

It is particularly contemplated that the lower surface of the ram iscoated with an elastically deformable material such as silicone rubberthat has heat resistance up to a temperature that is at least slightlyabove the highest temperature to which the glass will be heated when itis in place on the saddle and when it is being contacted by the lowersurface of the ram.

A further improvement contemplates that the elastically deformablematerial on the face of the ram may be bounded at its periphery by avertically positioned barrier cage which is formed in the same shape asthe outer periphery of the precast glass that is placed in the saddle,but which is slightly larger than the precast glass so as to extendbeyond the periphery thereof. It has been noted that particularly whenthe elastically deformable material such as silicone rubber is containedby the barrier cage, the deforming pressure within that material issubstantially constant throughout the material, and is substantiallyconstant in all directions, in much the same manner as occurs when afluid is pressurized.

The present invention also provides a method of laminating a polymerplastic film to a precast layer of glass, which comprises the followingsteps:

(a) placing a precast glass on a saddle which is contoured tosubstantially the identical contour of the lower surface of the precastlayer of glass, which saddle is adapted to transmit heat to and toabsorb heat from the precast layer glass;

(b) disposing a polymer plastic film horizontally above and over thesaddle;

(c) closing the distance between a contoured ram above the plastic andwhich has a contour on its lower surface substantially identical to thecontour of the upper surface of the precast layer of glass and thesaddle, towards the glass; so that the lower surface of the ram firstcontacts the polymer plastic film, and it then stretches the film andforces it into contact with the upper surface of the precast layer ofglass;

(d) increasing the pressure between the ram and the precast layer ofglass and the polymer plastic layer film up to a predetermined level,and then maintaining the pressure at that level;

(e) heating the combination of the precast layer of glass and thepolymer plastic film to a predetermined temperature, and maintainingthat temperature for a predetermined period of time;

(f) thereafter, cooling the combination of the precast layer of glassand the polymer plastic film to a predetermined temperature;

(g) thereafter, releasing the pressure of the ram against the by thenlaminated layer of polymer plastic film on the precast glass; and

(h) thereafter, removing the laminated plastic and precast glasscomposite structure from the saddle.

As noted above, the present invention contemplates that either, or both,of the ram and the saddle may be heated and cooled so as to quicklytransmit heat to and absorb heat from the combination of the glass andthe polymer plastic film. Moreover, one of the saddle and theram--usually the saddle--may be constantly heated, and theother--usually the ram--may be cooled sufficiently as to cause grossheat extraction away from the glass and polymer plastic combination.

As further described above, the present invention contemplates furtherthat the ram may be provided with an intermediate flexible layer of hardmaterial placed below the lower surface of the ram (which may be clampedso as to be movable therewith if the ram is movable), and an extendiblepiston is provided that acts against the upper surface of the flexiblematerial at the centre thereof so as to flex the flexible material fromthe centre thereof independently of the ram. In that case, the methoddescribed above may further include the steps of:

(i) prior to step (c), extending the extendible piston against theflexible material so as to first contact the clamped polymer plasticfilm at the centre thereof;

(j) thereafter, executing step (c) while, at the same time, graduallywithdrawing the extendible piston away from the flexible material whilemaintaining some pressure thereagainst, so that a progressively largerarea of the film will contact the precast glass; and

(k) thereafter, when the extendible piston has been fully withdrawn andthe film and glass are in contact over the entire area of the glass,proceeding with steps (d) et seq.

Where the composite glass/plastic film structure to be producedcomprises two layers of glass with a plastic film between them, whichplastic film constitutes a bonding agent for the two layers of glass andmay be PVB or polyurethane, the method of the present inventioncomprises the further steps of:

(l) after step (b), placing a further precast glass layer on the plasticfilm, where the further precast glass layer has a slightly differentcontour than the first precast glass layer so as to be capable of beingpressed onto the first precast glass layer; and

(m) thereafter, proceeding with steps (c) et seq.

Still further, the present invention contemplates the production of acomposite structure that comprises glass, a single layer of non-orientedPVB or polyurethane, a further layer of glass, and a further compositelayer of a non-oriented polymer plastic film together with an orientedpolymer plastic film--such as PVB/PET or polyurethane/PET--where the PETis remote from the second layer of glass and is on the inside surface ofthe composite structure when it is in use. In that case, the presentinvention provides further clamping means for that further compositeplastic layer, and the further steps of:

(n) after step (l), repeating step (b) with a composite polymer plasticfilm which may be PVB laminated with PET or polyurethane laminated withPET; and

(o) thereafter, proceeding with steps (c) et seq.

The present invention contemplates yet a further variation of theapparatus and methods discussed above, where the contact pressure of theram against the plastic, and of the plastic against the glass,progresses from one edge to the other. In this case, the face of the ramand the upper surface of the saddle--and the glass resting on it--areslightly tilted away from each other. The elastically deformable natureof the face of the ram assures a "rolling" contact line of the plasticto the glass as pressure between the ram and the saddle is increased.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in greater detail hereafter, havingregard to the accompanying drawings, in which:

FIG. 1 is a notional side view of a first embodiment of the apparatus ofthe present invention showing the principal components of the invention;

FIG. 2 is a notional side view of a further embodiment of the apparatusof the present invention, showing additional components of theinvention;

FIG. 3 is a notional side view of a yet further embodiment of the saddlecomponent of the present invention;

FIG. 4 is a top view of the saddle of FIG. 3;

FIG. 5 is a side view of a typical multi-laminar structure manufacturedin keeping with the teachings of the present invention;

FIG. 6 is a side view of yet a further multi-laminar structuremanufactured in keeping with the teachings of the present invention;

FIG. 7 is a notional side view of yet a further embodiment of theapparatus of the invention, particularly adapted to produce thestructures shown in FIGS. 5 and 6; and

FIG. 8 is a notional side view of a still further embodiment of theapparatus of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As noted above, the present invention provides an apparatus forlaminating polymer plastic film to glass; the present invention providesmethods for producing multi-laminar glass and plastic film structures;and the present invention provides such multi-laminar structures whenmade in keeping with the teachings hereof.

Several general principles concerning the present invention, theoperation of apparatus in keeping with the present invention, and themethods taught by the present invention, are now discussed:

In particular, the present invention is directed to laminating a polymerplastic film to glass (or glass to polymer plastic film) using pressureand heat. Particularly when the plastic film is such as PVB,polyurethane, PVB/PET, or polyurethane/PET, the working pressures andtemperatures are relatively low. For example, at a temperature ofapproximately 150 degrees C., PVB will adhere to glass in a matter of upto 360 seconds under pressures of up to 150 psi. This permits sufficienttime for the absorption of air at any interface with the PVB into thePVB. Once adhered, the plastic film remains adhered to the glass.Indeed, it is usual for plastic film adhered to glass in keeping withthe present invention to withstand pull-apart tensions of up to 30pounds per lineal inch.

In general terms, the present invention contemplates that a sheet ofglass of any given contour is supported on a saddle whose upper face issubstantially of the same contour as the lower face of the glass. Asnoted, that contour may be flat, simple curves, or it may have quitecomplex curvature. The saddle is lifted towards a ram (or the ram may belowered towards the glass) so that the face of the ram contacts thepolymer plastic film that has been interposed and positioned in placeabove the saddle and glass. The lower surface of the ram also has asubstantially identical curvature to that of the upper surface of theglass, but is generally more tightly curved--or a further flexible hardmaterial is movable with the ram but flexed downwardly towards the glassindependently of the ram, as described hereafter.

In any event, the lower surface of the ram is coated by an elasticallydeformable material, usually to a uniform thickness. In the generalembodiment of the present invention, as the distance between the ram andthe saddle is closed, the lower surface of the ram contacts the centreof the glass first, and then the contact area progresses outwardlytowards the periphery of the glass, so that contact of the plastic filmto the glass is assured while at the same time essentially precludingthe presence of other than very small air bubbles which can be absorbedinto the plastic film as it is being heated.

In another embodiment of the invention, the contact of the face of theram to the plastic film, and of the plastic film to the glass, firstoccurs at one edge thereof and progresses across the glass as thedistance between the ram and the saddle is closed. In either event, theelastically deformable material on the lower surface of the ram must besoft enought that it will deflect under pressure; and of course, theelastically deformable material must have a heat resistance that it willnot otherwise deform except by pressure at least up to temperaturesomewhat above the working temperature at which the non-oriented plasticfilm--PVB or polyurethane--is adhered to the glass. Generally, thatmeans that the elastically deformable material on the face of the rammust have heat resistance as described above up to at least about 160degrees C.

Reference is now made to the accompanying figures of drawings, wherelike components in the various figures are identified by identicalreference numerals.

Turning now to FIGS. 1 and 2, two slightly different embodiments areshown. The apparatus generally designated at 10 comprises a saddle 12above which a ram 14 is located. The face of the ram 14 is coated,usually to a uniform thickness, with a layer 16 of elasticallydeformable material such as silicone rubber. The silicone rubber mayhave a Shore hardness of about 50, being soft enough to deflect underthe pressure exerted by the ram as described hereafter.

A precast of layer of glass 18 is placed on the saddle 12, and above theprecast layer of glass 18 there is suspended and positioned in place alayer of polymer plastic film 20. The film may be positioned such as bya pair of clamps exerting force against each other, as shown at 28 and30 in FIG. 2.

For certain purposes as described hereafter, there may be a further thinlayer of glass or other hard surfaced material 22 interposed between theupper surface of the plastic film 20 and the lower surface of the ram16.

Within the saddle 12, there are located heating and cooling elements andducts generally indicated at 24. The heating may be electric heatingelements, and the cooling may be by circulating any suitable coolingliquid. In any event, the face of the saddle 12 which is in contact withthe precast layer of glass 18 must have good heat transfercharacteristics.

Similar heating and cooling elements and ducts 25 may be placed withinthe ram 14. It is assumed, in that case, that the structure of the ramalso has good heat transfer characteristics so that the heat may betransferred to or absorbed from the glass and polymer plastic film.

In each of FIGS. 1 and 2 (and FIGS. 7 and 8) arrows 26 and 27 are shown.They are intended to indicate the closing pressure between the ram 14and the saddle 12. It is understood that either the ram 14 may belowered, or the saddle 12 may be raised (as discussed above) and that ineither event the closing pressure between the ram 14 and saddle 12 iscreated as indicated by the arrows 26 and 27.

It is a feature of the present invention that at least the upper surfaceand the proximal region of the saddle 12 near the upper surface which isin contact with the glass 18, has essentially the same coefficient ofheat expansion and contraction as that of the glass. Thus, as the saddle12 is heated or cooled in order to heat or cool the glass 18, itssurface expands or contracts linearly--that is, sideways--at essentiallythe same rate as the glass. Of course, it is possible that in somecircumstances the upper face of the saddle 12 may be coated with apolymeric low friction coating so that a very small or limited amount ofslippage of the glass with respect to the saddle may be permitted. Thatpolymeric low friction coating may conveniently be a silicone compoundor PTFE.

Generally, at least the upper surface or portion of the saddle 12 ismade from stainless steel. It is particularly convenient to usestainless steel compound SS430, because that alloy has a coefficient ofheat expansion and contraction which is quite similar to that of glass.

Alternatively, the lower portion of the saddle 12, including thatportion of the saddle where the heating and cooling elements 24 arelocated, may be made from aluminum or other high heat conductivitymetal, which has a higher thermal conductivity than stainless steel,thereby assuring fast and efficient heat transfer to the glass and fastand efficient heat transfer away from the glass (cooling). Similar heattransfer structure and characteristics may be employed in the supportstructure for the ram 14, as necessary and required.

As noted, the lower surface of the ram 14 may be coated or covered withan elastically deformable material such as silicone rubber indicated at16. It is essential that the elastically deformable material should havea heat resistance up to a temperature at least slightly above thehighest temperature to which the glass 18 will be heated during thelaminating process. That temperature may be as high as 170 degrees C.,so the elastically deformable material such as silicone rubber shouldhave a heat resistance such that it does not distort due to heat alonebelow a temperature of at least about 170 degrees C. Moreover, thehardness of the silicone rubber is generally in the range of about 35 to65 Shore, generally about 55 Shore. The elastically deformable material,while having good heat resistance characteristics, may also have goodheat transfer characteristics so as to be able to transfer heat to andabsorb heat from (or both) the glass and polymer plastic filmcombination.

In a further aspect of the present invention, the entire periphery ofthe silicone rubber or other elastically deformable material 16 isbounded at its periphery by a vertically positioned barrier cage 36.Generally, the barrier cage 36 is formed in the same shape as the outerperiphery of the precast glass 18 which is placed on the saddle 12.However, the size of the elastically deformable material 16 andtherefore the size of the vertically positioned barrier cage 36--or atleast the area defined by the vertically positioned barrier cage 36--isslightly larger than the area of the precast glass 18. Thus, the barriercage 36 extends beyond the periphery of the precast glass 18.

A still further aspect of the present invention is also shownparticularly in FIG. 2. There, it will be noted that a further layer offlexible hard material such as glass 32--or stainless steel or othermaterials as discussed hereafter--is clamped in place below the siliconerubber 16 of the ram 14. Conveniently, the glass layer 32 is clamped bysuch means as the clamps 38 which are secured to the ram, so that theglass layer 32 is movable with the ram 14. However, an extendible piston34 is also provided, and it acts against the upper side of the glasslayer 32 at the centre thereof. Thus, it can be seen that if theextendible piston 34 is operated so as to extend downwardly it will flexthe flexible glass 32 from the centre thereof independently of the ram14, downwardly towards the precast glass 18 when placed in the saddle12.

The extendible piston 34 is arranged so that it may be withdrawn awayfrom the flexible glass 32 while still maintaining some pressure againstthe flexible glass 32, so that the glass 32 will progressively contact alarger area of the film 20 and of the glass 18 to which the film 20 isbeing laminated as the distance between the ram 14 and the saddle 12closes by lifting the saddle or lowering the ram.

Generally, the extendible piston 34 operates from an air cylinder (notshown), while the main pressure operating device for the ram 14 ishydraulically operated.

In general, the flexible hard material 32 is glass, which is most oftenpre-formed to the same contour as the upper side of the precast layer ofglass 18--the side to which the plastic polymer film 20 is to belaminated. In some circumstances, the flexible hard material 32 can befiberglass or epoxy, or stainless steel coated with fiberglass or epoxy.This is because the surface topography of the hard material will betransferred to the upper surface of the PET, or polyurethane if it is asingle layer, and it is generally not possible to polish stainless steelto a sufficiently smooth surface that aberrations on the surface willnot be noticed. Thus, fiberglass or epoxy coating cast against glasswill provide the surface finish necessary for the opticalcharacteristics that are required.

It should also be noted that, as the closing pressure between the ramand the saddle is being exerted against the film 20 and precast glass18, and the extendible piston 34 is withdrawn, the differential changesof the pressure of the flexible material 32 against the film exerted bythe extendible piston 34 and the ram 14 reduce from the centre outwards,until the flexible glass 32 assumes the same curvature as the lowersurface of the compressible material 16. This assures that air entrappedbetween the film 20 and the precast glass 18 is driven out, and thus abubble-free lamination of the film to the glass is assured.

As a practical matter, the saddle 12 may be placed on equalized floatpads or fluid bags 40, or otherwise made self-aligning, so thatalignment of the ram 14 with the saddle 12 and equal pressure over theentire surface of the precast glass 18 may be assured. Thus, when anapparatus as shown in FIG. 2 is being operated, where the lower surfaceof the flexible glass 32 touches the film 20 first at the centre of theprecast glass 18 and the contact area extends as the extendible piston34 is withdrawn and the ram 14 is lowered, or even as indicated in FIG.1, then the float equalization pads 40 may self-adjust to assure thatpressure over the surface is equalized.

The fluid bags 40 are interconnected as at 41, and are filled with afluid that may be a compressible gas but is more usually anon-compressible liquid. When pressure is exerted against any one bag orany portion of a bag by operation of the ram 14 or piston 34, so thatthe pressure is transmitted through the saddle 12 to the fluid bags 40,then the fluid in them will flow to any area where there is a lowerpressure, thus equalizing pressure in the fluid bags 40 as they supportthe saddle 12. A single fluid bag may be used in some instances.

In any event, as the ram 14 continues to be lowered and the extendiblepiston 34 retreats, then the float equalization exerted as a consequenceof the float pads or fluid bags 40 becomes more effective.

The assembly of the support for the saddle 12 as shown in FIG. 1 maycomprise an insulator layer 13 below the heating and cooling elements24, supported by a steel plate 15. That steel plate 15 is, in turn,supported by the fluid bags 40, which rest on a further steel plate orother table 17. The edges of the saddle 12 may be surrounded by afurther insulator 19, which serves to maintain a more even temperaturegradient across the area of the saddle 12.

The relatively soft PVB (or polyurethane) will in some respects act as agauge or shim so as to permit minor adjustments of the film and glasswith respect to the lower surface of the ram, and thereby assuring abubble-free lamination.

As noted above, it is a purpose of the elastically deformable rubber 16or other material to act as a pressure distributor to ensure evenpressure of the ram 14 against the film 20 and glass 18. Especially whenPVB is used as the laminating film, it will generally laminate underpressures of about 40 psi to about 150 psi at temperatures of 120degrees C. to 140 degrees C. Another purpose of the silicone rubber 16is, therefore, to act as an insulator so that when the heating andcooling elements 24 and/or 25 are activated, there is no significantloss of heat and therefore of energy. Generally, however, the heatingand cooling elements 24 are used, and then the silicone rubber is chosento have good insulative properties. Because of that circumstance, thetemperature of the silicone rubber 16 will lag that of the heated andcooled saddle 12.

A consequence of the above is that energy efficiencies of production ofmulti-laminar glass and polymer plastic film structures in keeping withthe present invention, when compared to the energy requirements of anautoclave as discussed above to produce exactly the same structure, maybe as much as 500% to 1000% more energy efficient.

Turning now to FIGS. 3 and 4, a further embodiment of the saddle of thepresent invention is shown. There, as before, the contour of the upperface of the saddle shown generally at 42 and the countour of the lowerface of the ram 14 (not shown) are each substantially identical to therespective lower and upper surface contours of the precast layer ofglass 18. However, the saddle 42 comprises a segmented face made up of anumber of segments 44 which are secured to a backing plate 46 by means48 which may be machine bolts or other suitable securing means. In thiscase the backing plate 46 is intended to operate cool, so that it doesnot undergo any significant dimensional changes. The heating and coolingelements 24 are installed in each of the segments 44; and they areinsulated from the backing plate 46 by an insulating layer 45.

The upper segmented face of the saddle 42 comprises a plurality ofsegments 44, and each segment is spatially isolated from all othercontiguous segments by gaps 50. The material of the segments 44 is suchas to have a high coefficient of heat transfer, for example aluminum.

The saddle 42 is thereby such that the integrated coefficient of heatexpansion over the area of the face of the saddle is essentially equalto that of the glass 18. Thus, there is substantially zero or verylittle gross expansion or contraction of the face of the saddle 42compared to the expansion or contraction of the precast glass 18 as eachis heated and cooled.

Needless to say, the structure of the ram 14 as described above,including the addition of the flexible glass 32 and extendible piston34, works equally as well with the segmented saddle 42 of FIGS. 3 and 4.

As noted, the present invention contemplates that the material of thenon-oriented polymer plastic film 20 may be PVB or polyurethane, andthat it may be laminated with PET. Moreover, the present inventioncontemplates that PVB or polyurethane may be used alone, where a furtherlayer of glass is to be laminated into the structure with the firstprecast glass. In that instance, a composite PVB/PET film cannot be usedbecause the glass would not adhere to the PET. FIG. 1 contemplates anadditional thin layer of glass 22 placed above the plastic film 20. Theglass 22 may serve two purposes: either it may act as an additional hardsurface interposed between the silicone rubber 16 and the plastic film20; or it may itself be intended to be laminated to the upper side ofthe plastic film 20 when it is PVB or polyurethane, for example. In thelatter case, the lamination of the glass 32 to the film 20 may occur intwo steps, so as to assure that the film 20 is adhered in a bubble freemanner to the glass 18; but on the other hand, if the curvature of theface of the silicone rubber 16 on the ram 14 is sufficiently tighterthan that of the upper face of the glass 18--the datum as far as theother lamina are concerned--then it is possible that the glass 32, thefilm 20, and the glass 18, may all be laminated in a single operation.This is discussed in more detail below, with special reference to FIGS.5 and 7.

The steps of the present invention have been discussed above. Thus,having regard to the recital of the steps noted above, step (a) callsfor the precast glass 18 to be placed on the saddle 12. Step (b)requires that the polymer plastic film 20 be clamped over the saddle;and step (c) calls for the distance between the contoured ram 14 havingthe flexible material 16 on its lower face and the saddle 12 to beclosed, so that the lower face of the ram first contacts the film 20 andthen stretches the film 20 and forces it into contact with the uppersurface of the precast layer of glass 18.

Thereafter, as recited, step (d) provides for the pressure between theram 14 and the precast layer of glass 18 and the plastic film 20 to beincreased up to a predetermined level, and then maintained at thatlevel. While the pressure is being maintained at the predeterminedlevel, step (e) provides that the saddle is heated to a predeterminedtemperature, and maintained at that temperature for a predeterminedperiod of time.

Thereafter, step (f) is followed to cool the saddle to a predeterminedtemperature, and then step (g) provides that the pressure of the ramagainst the plastic film 20--which is by then laminated to the precastglass 18--be released. Finally, step (h) provides for the laminatedplastic and precast glass composite structure to be removed from thesaddle 12.

As noted above, the present invention contemplates that either, or both,of the ram and the saddle may be heated and cooled so as to quicklytransmit heat to and absorb heat from the combination of the glass andthe polymer plastic film. Moreover, one of the saddle and theram--usually the ram--may be constantly heated, and the other--usuallythe ram--may be cooled sufficiently as to cause gross heat extractionaway from the glass and polymer plastic combination.

Having regard to the embodiment of the ram as shown in FIG. 2, thepresent invention provides for step (i) to be carried out prior to step(c), so that the extendible piston 34 is extended downwardly against theflexible material 32 so that the flexible material 32 first contacts thefilm 20 at the centre thereof. Afterwards, step (c) is carried outwhile, at the same time, the extendible piston 34 is gradually withdrawnaway from the flexible material 32 while maintaining some pressureagainst it. In this manner, a progressively larger area of the film 20will contact the precast glass--and, as discussed above, the contact ofthe film to the glass will be substantially bubble-free.

Thereafter, step (k) provides for the condition that when the extendiblepiston has been fully withdrawn and the film and glass are in contactover their entire area, then steps (d) et seq. are proceeded with.

As discussed, the present invention contemplates a structure such asthat shown in FIG. 5, which comprises the precast glass 18, a layer 52of non-oriented polymer plastic film which may be PVB or polyurethane,and a further layer of glass 54. To manufacture that structure, thepresent invention provides for the further steps (l) and (m) as follows:

Step (l) is carried out after step (b), and it involves placing afurther precast glass layer 54 on the plastic film 20; it being notedthat the further precast glass layer 54 has a slightly different contourthan the first precast glass layer 18 so as to be capable of beingpressed onto it. Thereafter, step (m) provides for steps (c) et seq. tobe proceeded with.

Such a structure as described immediately above may be used for awindshield, comprising two layers of glass secured one to the other bythe non-oriented polymer plastic film under heat and pressure asdiscussed.

The present invention further provides for a safety windshield or a sidewindow for an automobile which would comprise laminates of glass, afirst non-oriented polymer plastic film, a second laminate of glass, anda second composite film having non-oriented polymer plastic filmtogether with PET, where the second non-oriented plastic film is placedso as to be on inside surface of the safety windshield or side windowwhen in use. The first plastic film may be PVB or polyurethane; thesecond composite plastic film may be PVB/PET or polyurethane/PET withthe PET being remote from the second layer of glass--in other words, thePVB or polyurethane serves to laminate the PET to the second layer ofglass in the same manner as discussed above.

To manufacture that structure, shown in FIG. 6 having a first precastglass 18, a first plastic film 52, a second precast glass 54, and thesecond composite polymer plastic film 60, the present invention providesfor step (n) which is carried out after step (l), and which essentiallyrequires that step (b) be repeated using the composite plastic polymerfilm. Thereafter, step (o) provides for steps (c) et seq. to beproceeded with.

To more fully describe the steps taken to manufacture the structures ofFIGS. 5 and 6, reference is made to FIG. 7 which shows much the samefeatures as in FIG. 2. However, FIG. 7 shows a structure which, in theembodiment shown includes, those components indicated in the interval33, and which produces the multi-laminar structure of FIG. 6; andwithout the components shown at 33, the apparatus produces themulti-laminar structure of FIG. 5. It will be seen that the firstplastic film 52 is clamped between the clamps 28 and 30, with the secondprecast glass 54 being placed on it as discussed above. If the structureof FIG. 5 is being produced, then the additional components are notpresent, and steps (l) and (m) are carried out.

If, on the other hand, it is intended to produce the multi-laminarstructure of FIG. 6, then the additional clamping member 31 is in placeacting against clamp 30 to hold the second composite polymer plasticfilm 60 in place. Thereafter, steps (n) and (o) are carried out. Thus,in either event, to produce the structure of either FIG. 5 or FIG. 6, asingle clamping operation is carried out.

Finally, turning to FIG. 8, a further embodiment of the invention isshown where the contact pressure of the ram 14 against the plastic film20, and of the plastic film 20 against the glass 18, progresses from oneedge of the glass 18 to the other. Here, a slight tilt is effectedbetween the ram 14 and the saddle 12--and their opposed faces and theglass 18 sitting on the saddle 12--so that as the distance between theram 14 and the saddle 12 is closed, contact is first made by the ram 14against the plastic film 20 at the extreme right edge of the ram asindicated in FIG. 8. Thus, the ram first contacts the plastic film 20near the edge thereof, and in a position that is over the edge of theglass 18. As the distance between the ram 14 and the saddle 12 isclosed, and the closing pressure 26 and 27 continues in the directionsshown, a "rolling" contact line between the plastic film 20 and theglass 18 develops. That contact line moves progressively across theglass 18 from the right to the left edge as shown in FIG. 8, because ofthe elastically deformable nature of the layer 16 on the ram 14.Thereafter, as the distance between the ram 14 and the saddle 12 reachesa predetermined distance so that the pressure within the elasticallydeformable layer 16 on the ram 14 is constant across its entire area,then the heating cycle whereby heat is transferred quickly to the glass18 and plastic film 20--usually from the saddle 12--is initiated. Thetilt between the ram 14 and the saddle 12 is exaggerated for purposes ofillustration in FIG. 8; and in practice is a matter of fractions of adegree. The tilt may be accommodated by different sizes of fluid bags 40and 40A as indicated in FIG. 8, or by placing a shim under one side ofthe fluid bags or the table 17 or steel plate 15, as necessary andconvenient.

There has been described an apparatus for laminating polymer plastic toprecast glass, methods for achieving the laminated structures, and thestructures themselves. The scope of the present invention is defined bythe appended claims.

I claim:
 1. A method of laminating a layer of non-oriented polymerplastic to a precast layer of glass, comprising the steps of:(a)obtaining a precast layer of glass, said glass having a first face andsecond face; (b) placing said precast layer of glass on a saddle suchthat said first face of said precast layer of glass contacts an upperface of said saddle, which upper face is contoured to substantially theidentical contour of said first face of said precast layer of glass, andwhich saddle is adapted to transmit heat to and absorb heat from saidprecast layer of glass; (c) disposing a polymer plastic film at adistance away from said second face of said glass; (d) introducing acontoured ram and an intermediate layer of hard flexible material abovesaid polymer plastic film, said ram having a lower surface that iscontoured to substantially the identical contour of said second face ofsaid precast layer of glass, said intermediate layer having a surfaceinitially more convexly contoured than the lower surface of the ram andplaced below said lower surface of said ram so as to face said polymerplastic film; (e) closing the distance between said contoured ram andsaid polymer plastic film, such that a central portion of said initiallyconvexly contoured layer of hard flexible material first contacts acentral portion of said polymer plastic film and then continues tostretch and force said polymer plastic film into initial contact with acentral portion of said second face of said precast layer of glass andresultingly applying a pressure thereto; (f) increasing the pressurebetween said ram and said precast layer of glass so as to stretch andforce the plastic film into increasingly greater contact area with saidprecast layer of glass whereby the contour of the intermediate layerincreasingly conforms to the contour of the lower surface of the ram;(g) increasing the pressure between said ram and said precast layer ofglass up to a predetermined level, and maintaining the pressure at thatlevel; (h) heating said combination of the precast layer of glass andthe polymer plastic film to a predetermined temperature, and maintainingsaid combination of the precast layer of glass and the polymer plasticfilm at least at that temperature for at least a predetermined period oftime; (i) thereafter, cooling said combination of the precast layer ofglass and the polymer plastic film to at least a predeterminedtemperature; (j) thereafter, releasing the pressure of said ram againstthe by then laminated polymer plastic film and precast glass; and (k)thereafter, removing the laminated plastic and precast glass compositestructure from said saddle.
 2. The method of claim 1, wherein saidsaddle has high heat transfer characteristics, whereby said heating ofsaid combination of the precast layer of glass and the polymer plasticfilm to a predetermined temperature, and said cooling of saidcombination, occur quickly.
 3. The method of claim 1, wherein said ramhas high heat transfer characteristics, whereby said heating of saidcombination of the precast layer of glass and the polymer plastic filmto a predetermined temperature, and said cooling of said combination,occur quickly.
 4. The method of claim 1, wherein said intermediate layerof a hard flexible material is clamped together with said ram so as tobe movable therewith, and an extendible piston acts against the side ofsaid hard flexible material facing said ram at the centre thereof so asto flex said hard flexible material from a central portion thereofindependently of said ram;said method comprising the further steps of:(l) prior to step (e), extending said extendible piston against saidhard flexible material so as to first contact said polymer plastic filmat a central portion thereof; (m) thereafter, executing step (e) while,at the same time, gradually withdrawing said extendible piston away fromsaid flexible material while maintaining some pressure thereagainst, sothat a progressively larger area of said film will contact said precastglass; and (n) thereafter, when said extendible piston has been fullywithdrawn and said film and glass are in contact over the entire area,proceeding with steps (g) et seq.
 5. The method of claim 4, wherein oneof said saddle and said ram is constantly heated, and the other of saidsaddle and said ram is cooled sufficiently when required so as tothereby cool said combination of the pre-cast layer of glass and thepolymer plastic film, and thereby so as to cause gross heat transferaway from said combination of glass and the polymer plastic film beinglaminated thereto.
 6. The method of claim 5, wherein said saddle isconstantly heated.
 7. The method of claim 2, where an intermediate layerof a hard flexible material is clamped together with said ram so as tobe movable therewith, and an extendible piston acts against the side ofsaid hard flexible material facing said ram at the centre thereof so asto flex said hard flexible material from a central portion thereofindependently of said ram;said method comprising the further steps of:(l) prior to step (e), extending said extendible piston against saidhard flexible material so as to first contact said polymer plastic filmat a central portion thereof; (m) thereafter, executing step (e) while,at the same time, gradually withdrawing said extendible piston away fromsaid flexible material while maintaining some pressure thereagainst, sothat a progressively larger area of said film will contact said precastglass; and (n) thereafter, when said extendible piston has been fullywithdrawn and said film and glass are in contact over the entire area,proceeding with steps (g) et seq.
 8. The method of claim 4, wherein saidpolymer plastic film is a single layer chosen from the group consistingof polyvinyl butyral and polyurethane, wherein said intermediate layerof hard flexible material is a second precast layer of glass.
 9. Themethod of claim 7, wherein said polymer plastic film is a single layerchosen from the group consisting of polyvinyl butyral and polyurethane,wherein said intermediate layer of hard flexible material is a secondprecast layer of glass.
 10. The method of claim 4, further comprisingthe steps of:(o) after step (c), repeating steps (a) through (c) with asecond precast layer of glass having a first and second face and asecond polymer plastic film such that the second glass layer is disposedabove the first polymer film and the second polymer plastic film isdisposed above the second glass layer, with the second polymer plasticfilm chosen from the group consisting of polyvinyl butyral laminatedwith polyethylene terephthalate and polyurethane laminated withpolyethylene terephthalate; and (p) thereafter proceeding with steps (d)et seq, wherein all of the subsequent steps refer to the second polymerplastic film and the second precast layer of glass to form a glasscomposite comprising two layers of glass and two polymer films.
 11. Themethod of claim 7, further comprising the steps of:(o) after step (c),repeating steps (a) through (c) with a second precast layer of glasshaving a first and second face and a second polymer plastic film suchthat the second glass layer is disposed above the first polymer film andthe second polymer plastic film is disposed above the second glasslayer, with the second polymer plastic film chosen from the groupconsisting of polyvinyl butyral laminated with polyethyleneterephthalate and polyurethane laminated with polyethyleneterephthalate; and (p) thereafter proceeding with steps (d) et seq,wherein all of the subsequent steps refer to the second polymer plasticfilm and the second precast layer of glass to form a glass compositecomprising two layers of glass and two polymer films.